1. Technical Field
The present invention relates to a porous glass matrix producing burner and a porous glass matrix producing method.
2. Related Art
Various methods have been conventionally proposed for producing fiber optic matrices. Among these methods, OVD (Outside Vapor Phase Deposition) method is generally used. OVD method is known as a method by which it is relatively possible to obtain a fiber optic matrix having a desired refractive index distribution and by which it is possible to churn out fiber optic matrices having a large diameter.
In one example OVD method, at the first stage, while a starting matrix and a glass matrix producing burner are reciprocated with respect to each other, a flame including glass particles is sprayed from the glass matrix producing burner to the starting matrix to deposit glass particles (soot) on the starting matrix. At the next stage, the soot-deposited material is dewatered and sintered in an electric furnace to be turned into a transparent glass, as a result of which a fiber optic matrix is produced.
A concentric multiple tube burner made of silica glass has been used as the burner for synthesizing the deposits of glass particles. Because a concentric multiple tube burner cannot mix a glass material gas, a combustible gas, and a combustion improving gas sufficiently, it tends to result in producing an insufficient amount of glass particles. As a result, it has been impossible to increase the yield, and it has been difficult to synthesize glass particles at a high speed.
To solve this problem, Patent Document 1 proposes a multiple nozzle multiple tube burner. The multiple tube burner of Patent Document 1 has an annular combustible gas jetting opening around a material gas jetting port, and a plurality of small-diameter combustion improving gas jetting ports in the combustible gas jetting opening that are concentric with respect to the center axis of the material gas jetting port.
Many structures are proposed for the multiple tube burners of this type for further improving the deposition efficiency. For example, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5 are proposed for structures for small-diameter combustion improving gas jetting ports. Patent Document 6, Patent Document 7, and Patent Document 8 are proposed for optimization of the focal length of small-diameter combustion improving gas jetting ports. Patent Document 9, Patent Document 10, Patent Document 11, and Patent Document 12 are proposed for optimization of the gas flow rate and the gas linear velocity of a multiple tube burner.
[Patent Document 1] Japanese Patent No. 1773359
[Patent Document 2] Japanese Patent Application Publication No. 2003-206154
[Patent Document 3] Japanese Patent Application Publication No. 2004-331440
[Patent Document 4] Japanese Patent Application Publication No. 2006-182624
[Patent Document 5] Japanese Patent No. 3744350
[Patent Document 6] Japanese Patent Application Publication No. H5-323130
[Patent Document 7] Japanese Patent No. 3543537
[Patent Document 8] Japanese Patent Application Publication No. 2003-226544
[Patent Document 9] Japanese Patent No. 3591330
[Patent Document 10] Japanese Patent Application Publication No. 2003-165737
[Patent Document 11] Japanese Patent Application Publication No. 2003-212555
[Patent Document 12] Japanese Patent No. 3653902